The average kinetic energy of the molecules in a gas sample depends only on the temperature, . However, given the same kinetic energies, a lighter molecule will move faster than a heavier molecule, as shown in the equation for rms speed

rms speed=3ℳ⎯⎯⎯⎯⎯⎯⎯⎯⎯√
where =8.314 J/(mol⋅K) and ℳ is molar mass in kilograms per mole. Note that a joule is the same as a kilogram‑meter squared per second squared (kg·m2/s2).

What is the rms speed of O2 molecules at 371 K?
rms speed:
m/s
What is the rms speed of He atoms at 371 K?
rms speed:
m/s